Broadband wireless communication system is based on an orthogonal frequency division multiplexing (OFDM) scheme, an orthogonal frequency division multiple access (OFDMA) scheme or an orthogonal frequency division multiple access (OFDMA) scheme and enables fast data transmission in a manner of transmitting a physical channel signal using multiple subcarriers.
A downlink data type transmitted to a mobile station by a base station is mainly classified into a multicasting/broadcasting data type and a unicast data type. The multicasting/broadcasting data type can be used by the base station in transmitting such information as system information, configuration information, software upgrade information and the like to at least one or more groups to which non-specific/specific mobile stations belong. And, the unicast data type can be used by the base station in transmitting a request information to a specific mobile station or sending a message containing information (e.g., configuration information) which should be delivered to a specific mobile station only.
Meanwhile, an uplink data type transmitted to a base station, a different mobile station or the like by a mobile station consists of a unicast data type. The mobile station is able to send a message containing information, which will be finally delivered to a different mobile station, a server or the like, to the base station.
A conventional communication was mainly a communication performed between a mobile station used by a user and a base station. Yet, the development of communication technologies has enabled a machine-to-machine communication. The machine-to-machine (hereinafter abbreviated M2M) communication literally means a communication between one electronic device and another electronic device. In a broad sense, the M2M communication may mean a wire/wireless communication between electronic devices or a communication between a human-controllable device and a machine. Recently, the M2M communication may generally indicate a communication between electronic devices, i.e., a device-to-device wireless communication.
In the early 1990's, in which the concept of the M2M communication has been initially introduced, the M2M communication has been recognized as remote control or telematics and derivative markets of the M2M communication were very limitative. Yet, the M2M communication has grown rapidly for past few years and has been introduced into the globally noteworthy markets as well as Korean market. Specifically, in POS (point of sales) and security related application markets, the M2M communication has considerable influence on such field as fleet management, remote monitoring of machinery and equipment, smart meter for auto-measurement of operating time, consumed heat or electricity quantity on construction machinery equipment and the like. M2M communication in the future will be further utilized for various usages in connection with small-scale output communication solutionsfor conventional mobile communication, wireless high-speed internet, Wi-Fi, ZigBee and the like and may lay the foundation of expansion to B2C (business to consumer) markets instead of being confined to B2B (business to business) markets.
In the era of the M2M communication, every machine equipped with SIM card enables data transmission and reception and is capable of remote management and control. For instance, as M2M communication technology is usable for numerous devices and equipments including cars, trucks, trains, containers, auto-vending machines, gas tanks and the like, its application fields may reach far and wide.
As the number of application types of M2M devices keeps increasing, numerous M2M devices may exist within the same base station. When the numerous M2M mobile stations in idle state attempt random accesses, collisions occur more frequently to cause a problem that communication performance is degraded. Such problem may affect a conventional mobile station (e.g., HTC (human type communication)) as well as M2M mobile stations.
However, any efforts or attempts have not been made to research and develop a method of distributing random accesses of M2M mobile stations.